1. Field of the Invention
The present invention relates to a semiconductor device and a method of manufacturing such a semiconductor device, and more particularly to a semiconductor device with a semiconductor chip mounted thereon and a method of manufacturing such a semiconductor device.
2. Description of the Related Art
Generally, semiconductor chips are mounted on package boards of semiconductor devices in view of the environment in which they are used and the ease with which they are installed on the package boards. There are available various types of packages designed to meet the different sizes of semiconductor chip and the numbers of terminals thereof. If semiconductor chips have many terminals, then it is often customary to use packages of the BGA (Ball Grid Array) type with terminals arranged in a grid pattern on the lower surface of the package or packages of the LGA (Land Grid Array) type.
FIG. 1 of the accompanying drawings fragmentarily shows in cross section an internal structure of a conventional semiconductor device, and FIG. 2 of the accompanying drawings fragmentarily shows in cross section an internal structure of another conventional semiconductor device.
As shown in FIG. 1, the conventional semiconductor device, generally denoted at 101, has a semiconductor chip 102 mounted on surface interconnections 107 of a package board 105. With this structure, it is necessary to insulate the semiconductor chip 102 from the surface interconnections 107. It is the general practice to coat a solder resist layer 103 on the surface of the package board 105, and secure the semiconductor chip 102 to the solder resist layer 103 with an insulating adhesive layer 104 (first conventional structure).
According to a recent attempt, no solder resist is used, but, as shown in FIG. 2, a semiconductor chip 102 is insulated from surface interconnections 107 by only an insulating adhesive layer 104a by which the semiconductor chip 102 is secured in position (second conventional structure).
However, the above conventional structures have suffered the following problems:
(1) Problems of the First Conventional Structure (FIG. 1)
In recent years, an insulating resin tape is frequently used as an insulating base 106 of the package board 105 in order to reduce the size and thickness of the semiconductor device 101. However, when the solder resist layer 103 is formed, the package board 105 with the insulating resin tape used as the insulating base 106 tends to be distorted and warped due to the warpage of the tape itself and the heat hysteresis that is experienced when the semiconductor device is assembled. Particularly, if the insulating resin tape is of an elongate rectangular shape having a large area, then its feedability is greatly reduced due to the warpage, making it difficult to assemble the semiconductor device. Attempts to guard against the warpage and other difficulties have been responsible for an increase in the cost of the semiconductor device.
For example, if the package board 105 is in the form of an elongate strip, then a feel-to-reel feed system needs to be employed to supply the package board 105 to the manufacturing process. The feel-to-reel feed system has a supply reel, on which the package board 105 prior to being processed is wound, preceding a processing position for unreeling the package board 105, and a takeup reel following the processing position for winding the processed tape from the processing position.
If the package board 105 as processed into an elongate rectangular shape is to be supplied to the manufacturing process, then a dedicated fixing jig for processing the package board 105 into an elongate rectangular shape is required. While small severed pieces of package board may be supplied to the manufacturing process, it is cumbersome to handle those package board pieces and the efficiency with which to manufacture semiconductor devices is lowered.
(2) Problems of the Second Conventional Structure (FIG. 2)
The second conventional structure is problematic in that defects tend to occur in the manufacturing process because the semiconductor chip 102 and the package board 105a are insulated from each other by only the insulating adhesive layer 104a. For example, since it is difficult to control strictly the amount of an insulating adhesive to be supplied to form the insulating adhesive layer 104a, the supplied amount of the insulating adhesive is often liable to vary from time to time. Even when the insulating adhesive is supplied in a constant quantity, the coated thickness of the insulating adhesive layer 104a tends to differ from place to place due to slight pressure differences that occur when the semiconductor chip 102 is bonded by the insulating adhesive layer 104a. Another problem is that the applied adhesive may be forced out of place. Furthermore, if the insulating adhesive is coated by a nozzle, then air bubbles are likely to be trapped in the insulating adhesive layer 104a. 